The present invention relates to storm window units, and particularly to a metal frame storm window unit incorporating an expandable frame.
Recent rises in the cost of heating buildings have made it economical to increase the amounts of insulation used in construction of buildings. Windows in newer buildings are now furnished with thermally insulating double glazing which includes a thin air space between a pair of parallel panes. In older buildings, and particularly in older homes, however, windows were until recently provided with a single pane of glass, and separately mounted storm windows were used to provide additional control of heat loss.
In many areas of the country, buildings were previously not equipped with exterior windows, yet the cost of heating has recently made it highly desirable to provide the insulating qualities of a dead air space trapped between parallel sheets of glass in a window. This can be economically accomplished by mounting storm windows having modern frames of, for example, extruded aluminum, within the original casing of an existing window. In fact, storm windows can provide better insulation than double glazed windows, if they are properly and tightly installed, since they provide a thicker dead air space between the panes of glass.
There are, however, several problems related with installation of metal frame windows within the casings of preexisting single glazed windows. For example, in older buildings which have begun to sag with age, window casings have sometimes become slightly misshapen as a result of sagging of the building's walls. Standard sized storm windows, then, can not be used in such window openings without field modification of the storm window or repair of the window opening. If it is desired to custom build storm window units to fit in such window openings, precise measurements must be made and followed accurately in construction of each window unit. Since the window units are assembled in a shop before installation, there are several opportunities for errors in measurement, often resulting in storm window units which do not fit the opening properly. It then becomes necessary either to modify the storm window unit, sometimes resulting in an installation which is not particularly attractive in appearance, or to build a new window unit to the correct measurements. Neither of these courses of action is particularly economical of time or materials.
Particularly in the case of storm windows mounted on the interior side of a pre-existing house window, it is often desirable to remove the storm window and its frame completely, to improve appearance during warm weather or to facilitate repair of the primary window. With previously known interior mounted storm windows, particularly those which have been specially made to fit out-of-square window casings, this is frequently difficult.
What is needed, therefore, is a storm window unit which may be installed on the interior side of a pre-existing window, within the pre-existing window casing, despite some misalignment of the window casing, and despite errors in measurement of the window casing prior to construction of the storm window unit. It is also desirable to have such a storm window unit be efficient in performance and attractive in appearance, as well as economical to install.